Type Locality:

Lower Peace River, Alberta (56 deg 12'N, 117 deg 18'W).

Distribution:

The Shaftesbury Shale is about 170 m (558 ft) thick in the type area, but thickens to around 400 m (1,312 ft) in the area west of Fort St. John. The Shaftesbury Shale is recognized over most of the Peace River area of British Columbia and Alberta, but changes name when split into three parts by the Goodrich Sand near the foothills in British Columbia. It is recognized in the foothills of Alberta north of the Athabasca River.

Lithology:

A friable, dark marine shale with a band of fish scale bearing silts in the central portion, some thin bentonitic streaks and occasional ironstones in the Shaftesbury region; more silty in the British Columbia portion near Fort St. John, with ironstone nodules carrying large ammonites.

Relationship:

The contact with the ovens continental Dunvegan Formation is conformable and transitional both vertically and laterally. The contact with the underlying Peace River Formation is conformable, but a hiatus is indicated, as the Haplophragmoides gigas Zone is missing at the town of Peace River, although present in the subsurface to the east and present in part to the north. In the foothills of west-central Alberta the Shaftesbury equivalent overlies the Mountain Park Formation. The Shaftesbury is equivalent to the Hasler, Goodrich and Cruiser formations of the Pine River area, and to the upper Buckinghorse, Sikanni and Sully formations of the Sikanni Chief River in northeastern British Columbia. It is equivalent to the lower part of the Sunkay Member of the Blackstone Formation, and to beds immediately above and below the Fish Scale marker bed of the Colorado Shale, and to the lower part of the Labiche Shale of northeastern Alberta. Its American counterpart is the Mowry Shale.

History:

Dawson (1881) applied the name Fort St. John to shales underlying the Dunvegan Formation. McConnell (1893) gave the base of the Fort St. John Shale as the top of the Peace River Formation. To avoid re-definition of this shale interval between the Dunvegan and Peace River sandstones as the term Fort St. John Croup was expanded to include shales below the Peace River Sandstone, McLearn and Henderson (1944) introduced the term Shaftesbury Shale.

Other Citations:

Dawson, 1881; McConnell, 1893; McLearn and Henderson, 1944; Stelck, Wall and Wetter, 1958; Stott, 1961, 1968, 1981; Warren and Stelck, 1958.

References:

McLearn, F.H. and Henderson, J.F., 1944. Geology and oil prospects of the Lone Mountain area, British Columbia; Geological Survey of Canada, Paper 44-2.